In particular for the foundations of structural works, bored piles are produced in the ground. Initially a borehole is created in the ground which is filled with a suspension already during drilling or only after completion of the drilling works. This suspension can optionally be hardened by adding binding agents or exchanged for a hardenable medium in the borehole to form the bored pile.
The load bearing capacity of a bored pile is significantly influenced by the boundary layer between the bored pile and the adjacent ground. It is known that loose ground material which sediments or settles at the bottom of the borehole during creation of the borehole has a negative influence on the contact area and thus the load bearing capacity of the bored pile.
To remove such loose ground material from the borehole bottom it is known to lower an immersion pump as a cleaning device into the bore filled with suspension after completion of the drilling, with which immersion pump the loose ground material is sucked away from the bottom and removed from the borehole via a suction line.
In the case of such a cleaning device it can arise that loose ground material remains on the borehole bottom with increasing distance from the suction opening. Comprehensive cleaning of the borehole bottom is not therefore brought about with such a cleaning device.
It is further known to convey loose ground material away from the borehole mechanically for example by a drill bucket. However, a certain amount of loose ground material can remain at the bottom of the borehole with this mechanical excavation process.
EP 1 491 716 A2 discloses a drilling tool with a pumping means, with which removed ground material can be conveyed into a collecting container of the drilling tool.
A device and a method for filtering suspensions in boreholes follow from DE 28 07 917 A1. Filtered ground material is received in a collecting container within the filter device.